Classification of a large collection of whistles from Indo-Pacific humpback dolphins (Sousa chinensis)

Abstract

The whistle repertoires of some dolphin species have been characterised and classified both qualitatively and quantitatively [1, 2, 3, 4, 5]; however, given the extensive range of the species relatively little is known about the acoustic repertoire of the Indo-Pacific humpback dolphin, Sousa chinensis [6, 7], particularly those in South-east Asia. Quantitative classification methods have been developed using sub-sets of S. Chinensis whistles [8, 9, 10] but research aimed at classifying a more complete whistle repertoire of S. Chinensis through quantitative classification methods has not been reported. To address this, whistles produced underwater by six Indo-Pacific humpback dolphins kept by Underwater World Singapore Pte. Ltd. at Dolphin Lagoon, Sentosa, Singapore were recorded. The acoustic recordings were de-noised and the whistles ‘traced’ from the spectrogram time/frequency representation. They were then classified using PCA and k-means clustering.